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Before posting, please read https://www.cgsecurity.org/testdisk.pdf

I removed a drive from a RAID 1 pair, meaning to use it to install Windows on. So I deleted the ext4 partition, then created a new NTFS one. Then I deleted that as well to have a clean disk to install on.

Sometime later I managed to pretty thoroughly mung the remaining RAID drive, losing /home in the process.

Now I'd like to try to get that /home ext4 partition back on the un-RAIDed drive.

I know there's data still on the un-RAIDed drive, as I ran photorec and it found files and recovered them. Can I make this work? Is there a way to tell TestDisk what kind of filesystem to repair?

It's RAID of the mdadm variety. The system motherboard has a RAID controller on it, and there's support for RAID in the BIOS.

I wasn't the person who set up the RAID, and while I asked for the RAID to be broken (it wasn't), I wasn't the person who actually removed the secondary drive from the RAID. So I don't know if the drives were partitioned and then RAIDed, or RAIDed and then partitioned. My knowledge of the minutiae of RAID setup and configuration is minimal.

What I can tell you is that when I run a GPartEd live CD on the system, it can see the individual drives (/dev/sda etc) as well as the RAID image (/dev/md127).

This was RAID 1, so one drive is a duplicate of the other. There was only a single partition spanning the entire drive, which was (when in the raid configuration) mounted as /home.

There was another drive entirely holding the Linux filesystem root. System originally had one PATA system drive and two SATA drives, RAID 1, mounted as /home.

What makes me think it's EFI GPT is that that's what photorec reported finding when it started working on the disk.